1. Field of the Invention
The present invention relates to a semiconductor circuit, particularly to a semiconductor device excluding a malfunction due to negative noises.
2. Description of the Related Art
FIG. 12 shows a power-device-driving circuit (boost strap type) using a conventional HVIC and a circuit in the range from the level-shift section up to the high-side output in the HVIC. When driving a power semiconductors (such as MOSFET and IGBT) 100 and 101 half-bridge connected by a high-withstand-voltage integrated circuit (HVIC), most loads of the power semiconductor are inductive (L) loads such as a motor and a fluorescent lamp. Moreover, the middle point of half-bridge connection, that is, the high-side reference potential (VS) of an HVIC transitionally fluctuates toward the negative side to a GND (substrate potential of HVIC: lowest potential) under switching (particularly, when low-side output (driving lower arm) is turned on) because of also being influenced by a parasitic L component or the like due to a wiring or the like on a printed circuit board. Furthermore, in the case of an L load, because a two- or three-phase circuit is connected through the load in FIG. 12, the reference potential (VS) vibrates to the negative side only under switching of other phase.
When the reference voltage (VS) vibrates to the negative side and recoveries, the recovery current shown in FIG. 13 circulates through a level-shift resistor R from a VB terminal as the drain current of a level-shift high-withstand-voltage MOSFET (hereafter referred to as HVMOS). Therefore, the recovery current is erroneously recognized as a high-side input signal, thereby a high-side circuit malfunctions, an abnormal signal is output to the output (HO: upper-arm control signal) of the circuit, and a trouble such as a short circuit of arm) may occur. Level shift denotes level conversion required to drive a high-rated-voltage output device at several volts (control signal level of personal computer).
This malfunction may be caused by dv/dt to be applied to a high-side reference potential (VS). That is, when external dv/dt is applied to a parasitic capacity (Cp) present between the drain and the source of an HVMOS serving as a switching device for level-shifting a low-potential reference signal (GND of HVIC: substrate voltage) in an HVIC to a high-side reference potential (V) signal, a current of Ip=Cpxc3x97dv/dt circulates through the parasitic capacity. Thereby, the above current circulates through a level-shift resistor connected to a high-side power source (VB) and a voltage drop due to the current is input to the input device of a high-side level-shift signal. Resultantly, a high-side circuit outputs an abnormal signal.
For the above trouble, the following systems are proposed: a system for selecting a level-shift signal by a CR filter and a logic filter system (Japanese Unexamined Patent Publication No. 145370/2001) excluding simultaneous input of erroneous signals to a xe2x80x9cRS flip-flop circuitxe2x80x9d built in a high-side circuit by a logic circuit as shown in FIG. 14.
A semiconductor device for driving a power semiconductor according to one embodiment of the present invention includes, at its high-side section, a level-shift circuit, a voltage detector (NOT), a logic filter set (7), and a drive part (9). The level-shift circuit includes a resistance member (3,4,5,6) and a switching device (1,2). The resistance member includes a switching-on level-shift resistor which is divided into two first resistors (3,4) and a switching-off level shift resistor which is divided into two second resistors (5,6). The voltage detector (NOT) detects potentials of the both end of one(3) of the first resistors as signals Aon and Bon, and detects potentials of the both end of one(5) of the second resistors as signals Aoff and Boff. The logic filter set (7) logically excludes an error signals due to dv/dt from the signals detected by the voltage detector (NOT). The drive part (9) drives the power semiconductor based on the output of the logic filter set (7). When an output period of the signals Bon and Boff is longer than that of the signals Aon and Aoff, the logic filter set (7) does not outputs an abnomal signal.
A semiconductor device for driving a power semiconductor according to another embodiment of the present invention includes, at its high-side section, a level-shift circuit, voltage detectors (NOT1,NOT2,NOT3,NOT4), a logic filter set (7), and a drive part (9). The level-shift circuit includes a switching-on level shift resistor (10), a switching-off level-shift resistor (11) and a switching device (1,2). The voltage detectors (NOT1) and (NOT2) detect potentials of the end of the resistor (10) as signals Aon and Bon, and the voltage detectors (NOT3) and (NOT4) detect potentials of the end of the resistor (10) as signals Aoff and Boff . The logic filter set (7) logically excludes an error signals due to dv/dt from the signals detected by the voltage detector (NOT). The drive part (9) drives the power semiconductor based on the output of the logic filter set (7). Said voltage detor (NOT2) and (NOT4) have a threasould higher than those of the voltage detector (NOT1) and (NOT3). When an output period of the signals Bon and Boff is longer than that of the signals Aon and Aoff, the logic filter set (7) does not outputs an abnomal signal.